NEW YORK, Jan 23 (Reuters) - U.S. stocks fell modestly on Friday, pressured by some disappointing results from major multinational companies which offset optimism triggered by the European Central Bank’s recent decision to buy bonds and boost euro zone growth.

Wall Street jumped on Thursday, with the S&P 500 and Nasdaq returning to positive territory for the year, after the ECB detailed a bigger-than-expected bond-buying program to lift the region’s sagging economy and fight deflation.

With the ECB stimulus details known, U.S. corporate earnings will likely be the primary driver of trading over the next few weeks. A number of bellwether names have already disappointed, with revenue being a particular area of concern.

United Parcel Service Inc gave a fourth-quarter earnings outlook that was below expectations, citing a disappointing performance in U.S. domestic ground shipments. Shares slumped 9.7 percent to $103.21.

A pair of Dow components reported tepid results. McDonald’s Corp reported a drop in fourth-quarter comparable sales, though the decline was narrower than expected. General Electric Co reported lower sales in its oil and gas unit, though overall earnings rose.

McDonald’s added 0.2 percent to $91.13 while GE was up 0.4 percent at $24.38.

“Earnings have been a bit mixed this quarter. We’re not expecting a lot of multiple expansion,” said David Lafferty, chief market strategist of Natixis Global Asset Management in Boston, which has about $900 billion in assets under management.

“Valuations in the U.S. market are only okay, and you have to make sure you’re factoring in the impact from currencies, which will really be a headwind for multinationals.”

With 15 percent of S&P 500 companies having reported, 73.7 percent have topped earnings expectations while 53.9 percent have beaten on revenue, according to Thomson Reuters data. That compares with the long-term average of 63 percent for earnings and 61 percent for revenue.

Starbucks Corp rose 5.6 percent to $87.40 a day after the coffee chain reported same-store sales growth that was better than expected in its Americas region.

Crude oil fell 1 percent in the wake of the death of Saudi Arabia’s King Abdullah, though the country’s oil policies are expected to be unchanged. The commodity has dropped by more than half over the past six months.

For the week, the Dow is up 1.3 percent, the S&P 500 is up 1.8 percent and the Nasdaq is up 2.6 percent. All three are coming off three straight negative weeks.

Thursday’s rally took the S&P 500 above its 50-day moving average, a metric of near-term momentum that the benchmark index hasn’t closed above since Jan. 8.

At 9:56 a.m. (1457 GMT) the Dow Jones industrial average fell 59.51 points, or 0.33 percent, to 17,754.47, the S&P 500 lost 6.41 points, or 0.31 percent, to 2,056.74 and the Nasdaq Composite added 3.67 points, or 0.08 percent, to 4,754.07.

Declining issues outnumbered advancing ones on the NYSE by 1,522 to 1,249, for a 1.22-to-1 ratio on the downside; on the Nasdaq, 1,272 issues fell and 1,042 advanced for a 1.22-to-1 ratio favoring decliners.

The benchmark S&P 500 index was posting 52 new 52-week highs and 6 new lows; the Nasdaq Composite was recording 50 new highs and 19 new lows.